JPH0346849A - Priority control system for loop network - Google Patents

Abstract

PURPOSE:To execute the optimum priority control system without degrading the throughput of data transfer by separating channels for priority control and data transfer channels. CONSTITUTION:In the node where a transmission request occurs, the reserved priority level supplied from a loop 1 and the request priority level supplied from a data access control part 34 are compared with each other by a comparing circuit 33, and a selector 32 is controlled and the request priority level is sent as the reserved priority level to a priority reservation channel 13 if the request priority level is higher. If the request priority level is not higher or the transmission request does not exist, the received reserved priority level is allowed to pass as it is. Consequently, the value of the requested highest priority level is supplied to the priority reservation channel 13 after one circulation of the loop, and the priority control part of a loop master 2 sets this value to a priority control channel 12, and the multiple address is performed in all nodes.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to priority control of loop networks.

(Prior Art and Problems to be Solved by the Invention) There are two typical types of priority control in a loop network.

One is specified by IEEE802.5,
This is done by setting priority information in the access control field of the header of the data frame. Each node updates its own transmission request priority to its own value if it is higher than the priority indicated by the reservation subfield of the data frame being passed. The token holding node sets the priority reservation value written in the header of the data frame it has sent out as the token priority in another subfield, and sends the token frame to the loop. This method relies on token control in which a token holding node issues a token after the header of its own outgoing data frame has gone through a loop. With this token control method, as the loop speed becomes faster or the loop transmission path length becomes longer, transmission often ends before the header is returned.
It is known that throughput is significantly reduced. Therefore, although it has the excellent feature of being able to set the highest priority among the requested priorities while the header goes around once, it has the problem that it is not suitable for high-speed loop networks.

Another priority control is ANSI (American National Standards Institute)
FDDI (Fiber Dis
Tributed Data Interface), and is intended for networks with a high loop speed of 100 Mbps. In order to avoid the above-described drop in throughput, this network adopts a method in which the token signal is released at the same time as the transmission ends, unlike the above-described method. However, since the above-mentioned priority control cannot be implemented, control based on the circulation time of the token signal is adopted. That is, if the token circulation time is long, it means that the traffic on the loop is high, so a node that has a request to transmit a data frame with a low priority does not capture the token signal.

In this method, if the token signal circulation time is not long enough to restrict transmission of lower priority, even if a transmission request of higher priority occurs, it cannot be transmitted before a transmission request of lower priority, and There is a problem that the response time becomes long.

Therefore, the present invention provides a loop network priority control method that does not reduce data frame transfer throughput even if the transmission path speeds up, and can shorten the response time to a high priority transmission request. There is a particular thing.

(Means for Solving the Problems) In the loop network priority control system of the present invention, the loop transmission path has a priority channel, a priority reservation channel, and a data transfer channel by time division, and one loop network is provided with a priority channel, a priority reservation channel, and a data transfer channel. The master node transmits information indicating the lowest priority to the priority reservation channel, and the slave node accommodating the terminal sends information indicating the lowest priority to the priority reservation channel, and the slave node accommodating the terminal sends information indicating the lowest priority to the priority reservation channel. If not, the main node writes its own priority information to the priority reservation channel, receives the priority information of the priority reservation channel that has passed through the loop, and broadcasts this priority information via the priority channel. The information is supplied to all slave nodes, and each slave node device compares the priority information of the priority channel and, if its own transmission request priority is the same or higher, activates transmission right acquisition control for the data transfer channel. .

Further, in the loop network priority control system of the present invention, the loop transmission path has a priority channel, a priority reservation channel, and a data transfer channel in time division, and the priority reservation channel corresponds to the priority number N and has N bits. The master node, which has a long length and is provided in the loop network, transmits with all bits of the priority reservation channel turned off (for example, 0), and the slave nodes accommodating terminals transmit their own transmission requests with priority. The main node turns on (for example, 1) a bit in the priority reservation channel corresponding to the
The N-bit priority information of the priority reservation channel that has gone through the loop is received, and the highest priority among the turned-on priorities is broadcast to all slave nodes via the priority channel, and each slave If the node compares the priority information of the priority channel and its own transmission request priority is the same or higher, it activates transmission right acquisition control for the data transfer channel.

As described above, by separating the channel for priority control and the data transfer channel, an optimal priority control method can be implemented without reducing the data transfer throughput.

(Example) FIG. 1 shows the configuration of a loop network, and FIG. 2 shows slotted transmission frames on a loop transmission path. The loop network is composed of a loop master 2 and a plurality of nodes 3.4.5.6, which are interconnected by a loop 1. The transmission frame of loop 1 is divided into fixed length slots, the slot payload part is used as a data transfer channel 11, and a part of the slot header is allocated to a priority channel 12 and a priority reservation channel 13.

FIG. 3 shows an example of the configuration of the loop master 2, and FIG. 4 shows an example of the configuration of each node. Note that the loop master 2 is equipped with a delay control circuit 24 for making the loop-to-circular propagation delay time of the information on the data transfer channel 11 an integral multiple of the slot, but in order to simplify the drawing, the third In the figure, parts related to the function of transmitting data such as packets are not shown.

The multiplexing circuit 21 of the loop master 2 and the multiplexing circuit 31 of the node each have a data transfer channel 11 operated manually.
, priority channel E2, and priority reservation channel 13 to send the slot to assembly loop 1.

Loop master separation circuit 22 and node separation circuit 32
spreads the slot signal to a data transfer channel 11, a priority channel 12, and a priority reservation channel 13.

In the loop master 2, the reservation priority (1) is stored in the register 25.
The lowest value is set to 0 (in this case, the larger the value, the higher the priority is) (displayed in 0 decimal notation), and is sent for each slot.

In the node where the transmission request has occurred, the comparison circuit 33 compares the reservation priority supplied from loop 1 and the request priority supplied from the data access control unit 34, and if the request priority is higher, the selector 32 and sends the request priority to the priority reservation channel 13 as the reservation priority. If the request priority is not higher, or if there is no transmission request, the received reservation priority is passed through as is.

An example will be explained in which a communication request with a priority of 2.1.3 occurs in nodes 3, 4, and 6, respectively. In node 3, the value of the reservation priority channel 13 is set to 2, in node 4, which has a lower request priority, the reservation priority of value 2 is passed through as is, and in node 6, the reservation priority of value 3 is set.

Therefore, the priority reservation channel 13 after the loop-tour is:
The requested highest priority value of 3 is provided. The priority control unit 23 of the loop master 2 sets this value on the priority control channel 12 and broadcasts it to all nodes. node 3.4
In the data access control unit 34, since its own request priority is smaller than the value 3 of the priority control channel 12,
Do not activate transmission right acquisition control. Since the data access control unit 24 of the node 6 has the same request priority value as 3,
In order to access the data transfer channel 11, transmission right acquisition control is activated. Note that the present invention relates to priority control, and does not limit access control to the data transfer channel 11 or transmission right acquisition control. For example, a slotted ring system in which transmission rights are granted for each slot, or a data transfer channel 11
can be used as one packet loop, and a known control method such as a token passing method can be used.

Next, another embodiment will be described using FIGS. 3 and 5. The difference from the previous embodiment lies in the method of setting reservation priority. The reservation priority channel 13 has a 4-bit configuration, and as shown in FIG. 5, the reservation priority channel 13 is developed into 4 bits and processed in each node. The number of bits 4 corresponds to the number of priority levels. The loop master 2 sets each bit of the 4-bit register 25 to 0 (binary representation), which means that there is no request. node 3.4
．． 5 is a transmission request with a priority of 1.2.1, respectively, the value with the bit position corresponding to the priority set to 1, that is, 0001.0010.0001 (binary table E) is set in each register 36. do. A node without a transmission request sets 0000. The OR circuit 35 is a circuit that outputs the logical sum of each bit of the register 36 and the bit-expanded manual signal of the reservation priority channel 13, that is, it overwrites the logical sum. In this case, node 3 outputs 0001. At node 4, the 0 received from loop 1
The logical sum of 001 and the set value 0010 of the register 36 is taken, and 0011 is output. At node 5, 0010 is overwritten, but the output of the OR circuit 35 does not change to 0011. Based on the received 4-bit priority reservation information 0011, the loop master 2 determines that the requested highest priority is 2 since the most significant bit set to 1 is 2. This value is then broadcast to all nodes via the priority channel 12, as in the previous embodiment.

FIG. 6 shows an example of the configuration of a transmission frame that is not slotted. Even in such a transmission frame configuration, priority reservation channel 13 and priority channel 12 are set in the determined fields. It will be clear that by providing the data transfer channels 11 and the like independently, the same effects as in the embodiments described above can be obtained.

(Effects of the Invention) As explained above, according to the present invention, the following (a) to (
The effect of c) can be obtained.

(b) The highest requested priority of each node can be determined while the priority control information goes around the loop without affecting the access protocol for data transfer.

(O) The determined priority can be notified to the nodes (5, . . . each) while the priority control information goes around the loop without affecting the access protocol for data transfer.

(c) It is possible to give a transmission opportunity to a high priority transmission request with a short response time.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the loop network of the present invention,
2 and 6 are diagrams showing the structure of a transmission frame of a loop transmission path, FIG. 3 is a diagram showing an embodiment of a loop master used in the present invention, and FIGS. 4 and 5 are diagrams showing an embodiment of a node. FIG. In the figure, l is a loop, 2 is a loop mask, 3.4.
5.6 is a node, 21.31 is a multiplex circuit, 22.32 is a separation circuit, 24 is a delay control circuit, 25.3G is a register, 23 is a priority control section, 34 is a data access control section, 3
3 is a comparison circuit, 32 is a selector, and 35 is an OR circuit.

Claims (3)

[Claims] (1) The loop transmission path uses priority channels by time division.
The main node, which has a priority reservation channel and a data transfer channel and is provided in the loop network, sends information indicating the lowest priority to the priority reservation channel, and slave nodes accommodating terminals send their own transmission requests. is higher than the priority of the received priority reservation channel,
or if it is not low, writes its own priority information to the priority reservation channel, and the main node receives the priority information of the priority reservation channel that has gone through the loop, and broadcasts this priority information via the priority channel. A priority control method for a loop network characterized by supplying information to all subordinate nodes. (2) The loop transmission path uses priority channels by time division.
It has a priority reservation channel and a data transfer channel, and the priority reservation channel corresponds to the priority number N and has a length of N bits, and one main node provided in the loop network can read all of the priority reservation channels. The slave node that accommodates the terminal turns on the bit in the priority reserved channel that corresponds to the priority of its own transmission request, and the main node transmits the signal with the bit in the priority reserved channel that has completed one loop. A loop network priority control method characterized by receiving N-bit priority information and broadcasting the highest priority among the turned-on priorities to all slave nodes via a priority channel. . (3) According to claim (1) or (2), the loop transmission path is divided into fixed length slots, and a part of the header field of the slot is allocated to the priority channel and the priority reservation channel. priority control method for loop networks.